1. Field of Invention:
This invention relates to an ultrasonic welding horn provided with variable weights which can be removed and added to the horn in order to achieve a uniform distribution of the amplitude of ultrasonic vibration across the face of the worksurface of the horn.
2. Description of the Prior Art:
Ultrasonic welding may be used for several purposes, including the joining of metals or plastics. Ultrasonic welding is often used in applications where high temperatures would be impractical, such as in connecting fine wires to microchips, sealing plastic bags and hermetically closing toothpaste or similar tubes. The application of a high frequency of vibration is used in place of the application of heat causing the intermolecular bonding of overlapping worksurfaces.
In applications where a broad area must be welded, as in the aforementioned examples of sealing a plastic bag or the rolled end of a toothpaste-like tube, care must be taken to provide a uniform weld lest any portion of the welded area not adhere to itself, thus frustrating an aesthetic and hermetic seal.
In order to obtain uniform amplitude of vibration in the ultrasonic welding horn, it was recognized that the welding horn should be balanced so that its wave energy is distributed uniformly in its attachment to a sound wave booster or amplifier which in turn is connected to the source of ultrasonic energy. This has been accomplished in the prior art by carefully machining the horn to achieve the balance. More precisely, it was normal practice to cut grooves in the input side of the horn in order to remove whatever material necessary to achieve such a balance. Such a process is expensive and does not allow for later adjustment.